Wuxal amino (Bio stimulant) improved growth and physiological performance of tomato plants under salinity stress through adaptive mechanisms and antioxidant potential

In the present study, ameliorative capabilities of wuxal amino (bio stimulant) under salt stress has been investigated through adaptive mechanisms and antioxidant potential in tomato plants. In the experiment, two different concentrations (2 cm L^-1 and 3 cm L^-1) of wuxal amino through foliar application and soil irrigation were applied to the salt (150 mM) treated tomato plants and then morphological traits, photosynthetic pigments, osmolytes, secondary metabolites, oxidative stress and antioxidant enzymes activity were assessed at 60 days after planting. The results revealed that salt stress decreased the growth parameters, photosynthetic pigments, soluble sugars and soluble protein whereas, content of proline, ascorbic acid, total phenols, malondialdehyde, hydrogen peroxide and the activity of antioxidant enzymes activity increased under salt stress. Moreover, Wuxal amino application through foliar or soil to salt stressed plants improved morphological traits, photosynthetic pigments, osmolytes, total phenol and antioxidant enzymes activity. Interestingly, the deleterious impact of salinity on tomato plants were significantly reduced and it can be evident from reduced MDA and H₂O₂ levels. These responses varied with the mode (foliar or soil) of application of Wuxal amino under different concentrations (2 cm L^-1 and 3 cm L^-1). It was concluded that application of Wuxal amino (2 cm L^-1, foliar) and (3 cm L^-1; soil) proved best and could be commercially used as eco-friendly tool for the protection of tomato plants grown under salinity stress.     

Vasopressin and nitric oxide synthesis after three days of water or food deprivation

Nitric oxide has been suggested to be involved in the regulation of fluid and nutrient homeostasis. In the present investigation, vasopressin and nitric oxide metabolite (nitrite and nitrate) levels were determined in plasma of male Wistar rats submitted to water or food deprivation for three days. Hematocrit and plasma sodium showed marked increase in dehydrated and starved rats. Potassium levels and plasma volume decreased in both treated groups. Plasma osmolality and vasopressin levels were significantly elevated in water deprived (362.8 +/- 7.1 mOsm/kg H2O, 17.3 +/- 2.7 pg/ml, respectively, p < 0.001) rats, but not in food deprived (339.9 +/- 5.0, 1.34 +/- 0.28) rats, compared to the controls (326.1 +/- 4.1, 1.47 +/- 0.32). The alterations observed in plasma vasopressin levels were related to plasma osmolality rather than plasma volume. Plasma levels of nitrite and nitrate were markedly increased in both water and food deprived rats (respectively, 2.19 +/- 0.29 mg/l and 2.22 +/- 0.17 mg/l versus 1.33 +/- 0.19 mg/l, both p < 0.01). There was a significant negative correlation between plasma nitrite and nitrate concentration and plasma volume. These results suggest that both dehydration and starvation increase plasma nitric oxide, probably by activation of nitric oxide synthases. The release of nitric oxide may participate in the regulation of the alteration in blood flow, fluid and nutrient metabolism caused by water deprivation or starvation.     

Regulation of durum wheat Na<Superscript>+</Superscript>/H<Superscript>+</Superscript> exchanger TdSOS1 by phosphorylation

We have identified a plasma membrane Na⁺/H⁺ exchanger from durum wheat, designated TdSOS1. Heterologous expression of TdSOS1 in a yeast strain lacking endogenous Na⁺ efflux proteins showed complementation of the Na⁺- and Li⁺-sensitive phenotype by a mechanism involving cation efflux. Salt tolerance conferred by TdSOS1 was maximal when co-expressed with the Arabidopsis protein kinase complex SOS2/SOS3. In vitro phosphorylation of TdSOS1 with a hyperactive form of the Arabidopsis SOS2 kinase (T/DSOS2∆308) showed the importance of two essential serine residues at the C-terminal hydrophilic tail (S1126, S1128). Mutation of these two serine residues to alanine decreased the phosphorylation of TdSOS1 by T/DSOS2∆308 and prevented the activation of TdSOS1. In addition, deletion of the C-terminal domain of TdSOS1 encompassing serine residues at position 1126 and 1128 generated a hyperactive form that had maximal sodium exclusion activity independent from the regulatory SOS2/SOS3 complex. These results are consistent with the presence of an auto-inhibitory domain at the C-terminus of TdSOS1 that mediates the activation of TdSOS1 by the protein kinase SOS2. Expression of TdSOS1 mRNA in young seedlings of the durum wheat variety Om Rabia3, using different abiotic stresses (ionic and oxidative stress) at different times of exposure, was monitored by RT–PCR.     

A constitutively active form of a durum wheat Na+/H+ antiporter SOS1 confers high salt tolerance to transgenic Arabidopsis

Key message

Expression of a truncated form of wheat TdSOS1 in Arabidopsis exhibited an improved salt tolerance. This finding provides new hints about this protein that can be considered as a salt tolerance determinant.

Abstract

The SOS signaling pathway has emerged as a key mechanism in preserving the homeostasis of Na⁺ and K⁺ under saline conditions. We have recently identified and functionally characterized, by complementation studies in yeast, the gene encoding the durum wheat plasma membrane Na⁺/H⁺ antiporter (TdSOS1). To extend these functional studies to the whole plant level, we complemented Arabidopsis sos1-1 mutant with wild-type TdSOS1 or with the hyperactive form TdSOS1?972 and compared them to the Arabidopsis AtSOS1 protein. The Arabidopsis sos1-1 mutant is hypersensitive to both Na⁺ and Li⁺ ions. Compared with sos1-1 mutant transformed with the empty binary vector, seeds from TdSOS1 or TdSOS1?972 transgenic plants had better germination under salt stress and more robust seedling growth in agar plates as well as in nutritive solution containing Na⁺ or Li⁺ salts. The root elongation of TdSOS1?972 transgenic lines was higher than that of Arabidopsis sos1-1 mutant transformed with TdSOS1 or with the endogenous AtSOS1 gene. Under salt stress, TdSOS1?972 transgenic lines showed greater water retention capacity and retained low Na⁺ and high K⁺ in their shoots and roots. Our data showed that the hyperactive form TdSOS1?972 conferred a significant ionic stress tolerance to Arabidopsis plants and suggest that selection of hyperactive alleles of the SOS1 transport protein may pave the way for obtaining salt-tolerant crops.     

Influence of Cadmium Exposure on Growth and Fecundity of Freshwater Mosquitofish Gambusia affinis: In Situ and In Vivo Studies

This study aims to investigate the effect of cadmium (Cd) exposure on growth and fecundity of mosquitofish Gambusia affinis. For this purpose, two natural populations of pregnant females of G. affinis captured from two sites were differently contaminated with Cd (S1 present Cd levels 5-fold higher than S2) and a sublethal exposure to 0.4 mg CdCl(2)/L (10% of LC(50)) during 56 days was conducted in vivo. The length-weight regression revealed a significant difference in the growth between these two populations. A significant difference in fecundity was also noted between the two populations. Indeed, the embryo numbers in pregnant females captured from S1 are significantly higher than those noted in pregnant females from S2 (21.17±5 and 7.97±2.12, respectively; p<0.05). Following Cd exposure, we noted a growth perturbation resulting in lower values of both indices BWG and SGR following 7 and 21 days (-5.21 and -1.18 for BWG, and -2.09 and -0.46 for SGR, respectively) and a recuperation of growing weight at 42 and 56 days (1.32 and 1.71 for BWG, and 0.45 and 0.54 for SGR, respectively). For CF index, we observed a significant difference (p<0.05) between control and Cd groups at 7 and 21 days of exposure, and at 21 and 56 days respectively for HSI and GSI indices. Furthermore, Cd contents in both tissues (liver and yolk sac) and fractions (cytosolic and membrane) are significantly different between groups during experimentation. In addition, the Cd contents noticed in the liver membrane fraction are significantly higher than those noted in the yolk sac tissue. The MTs levels revealed a significant difference between the control and Cd groups. In liver tissue, a significant difference was noted, in MTs levels, during the Cd exposure (7, 21, 42, and 56 days) while in the yolk sac tissue the difference was noted at 42 days of exposure. Taken together, these results imply the potential negative effect of Cd on physiological status of G. affinis as evidenced by decreasing growth and fecundity rate.     

Chemical composition and acaricidal properties of Deverra scoparia essential oil (Araliales: Apiaceae) and blends of its major constituents against Tetranychus urticae (Acari: Tetranychidae)

The essential oil of Deverra scoparia Coss. & Durieu was investigated for its acaricidal activity against the worldwide pest twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). The essential oil was analyzed by fast gas chromatography (GC) and GC-mass spectrometry. The activities of its individual and blended constituents were determined. Our study showed that female mortality increased with increasing D. scoparia oil concentrations, with LD50 and LD90 values at 1.79 and 3.2 mg liter(-1), respectively. A reduction in fecundity had already been observed for concentrations of 0.064, 0.08, and 0.26 mg liter(-1) D. scoparia essential oil. Ten major components, comprising 98.52% of the total weight, were identified; a-pinene was the most abundant constituent (31.95%) followed by sabinene (17.24%) and delta3-carene (16.85%). The 10 major constituents of D. scoparia oil were individually tested against T. urticae females. The most potent toxicity was found with alpha-pinene, delta3-carene, and terpinen-4-ol. The presence of all constituents together in the artificial mixture caused a significant decrease in the number of eggs laid by females, at 0.26 mg liter(-1) (11 eggs), compared with the control (50 eggs). The toxicity of blends of selected constituents indicated that the presence of all constituents was necessary to reproduce the toxicity level of the natural oil.     

Salt stress reveals differential physiological,biochemical and molecular responses in <Emphasis Type="Italic">T. monococcum</Emphasis> and <Emphasis Type="Italic">T. durum</Emphasis> wheat genotypes

Salt stress responses implicate a complex mechanism and differ from plant species to another. In this study, we analyzed the physiological, biochemical and molecular responses to salt stress of the diploid wheat (T. monococcum) and compared to the tetraploid wheat (T. durum). Our results showed that the diploid wheat cultivar (cv. Turkey) is relatively tolerant to different salt stress conditions than the tetraploid wheat cultivar (cv. Om Rabia3). This tolerance was manifested by significant germination, plant growth and uptake of water generating cell turgor and development. Moreover, total chlorophyll content was higher in the diploid wheat than that in the tetraploid wheat. The Na⁺ content in leaf blade of the cv. Om Rabia3 was significantly higher than that of the cv. Turkey, suggesting that the diploid cultivar accumulates less toxic sodium in the photosynthetic tissues. This mechanism could be explained by the recirculation of the toxic ions Na⁺ into the xylem sap by SOS1 protein, which coordinates with HKT-like proteins to reduce the accumulation of Na⁺ ions in leaf blade. Interestingly, the expression of the three genes SOS1, HKT and NHX was enhanced under salinity especially in leaf blade of the cv. Turkey. Moreover, this wheat cultivar induced the antioxidative enzymes CAT and SOD activity more efficiently than the other cultivar.     

Restoring degraded arid Mediterranean areas with exotic tree species: Influence of an age sequence of Acacia salicina on soil and vegetation dynamics

Acacia salicina Lindl. is an Australian leguminous tree widely planted outside its original distribution as a multi-purpose species, and successfully establishes on degraded areas. The objective of this study was to determine how an age sequence of 3, 5, 9 and 13-year-old A. salicina plantations affected soil properties and flora diversity of an arid Mediterranean steppe. Soil samples were taken from the upper 10 cm of soil under tree canopies and in the associated open spaces. The results showed that tree establishment and development enhanced soil contents of total C, total N, available P and exchangeable K⁺, Ca²⁺, Mg²⁺ and Na⁺. These trends increased significantly with increasing plantation age. At the same time A. salicina facilitated the colonization and development of understory vegetation. Indeed, the number of plant species, the total plant cover, the perennial species density, the plant biomass and the diversity all attained higher values under tree canopies and increased with increasing plantation age. The soil dynamic under 13-year-old A. salicina plantations reflected two phases in the restoration sequence, characterized by nominal changes during tree establishment (0–5 years) and showing marked and rapid changes associated with the start of canopy closure (5–13 years). A. salicina establishment could be an effective and applicable measure to restore soil and vegetation and control desertification in the Mediterranean arid steppes.